Why do so many police officers act like filming them is against the law?

It's an appropriate question to ask. Just today it turns out that the police appear to have deliberately lied in the case of the undercover policeman (who was married) who had a sexual relationship with someone in his undercover role. First they denied it. Then they said yes their policeman did have a sexual relationship with someone in his role as being undercover, but that sexual relationship would never have been sanctioned or agreed with. Now it appears that this undercover policeman's bosses both sanctioned it and knew about it. It's totally unacceptable deceit and it undermines the whole role of the police in society and all those decent proper hard working policemen and policewomen. It's a disgrace.